Electrochemistry of a urea-functionalized calix[4]diquinone sulfate-anion selective receptor

A new class of neutral ligands is synthesized and studied for the binding properties with anions by electrochemical methods. The binding of calix[4]diquinone 1 with HSO₄^? causes a large negative shift of the electrode potentials of the calix[4]diquinone. This novel neutral anion receptor 1 binds anions through hydrogen-bonding and shows high selectivity for HSO₄^? over H₂PO₄^?, Cl^?, and CH₃CO₂^?. The selectivity of HSO₄^? over H₂PO₄^?, Cl^?, and CH₃CO₂^? may be attributed to the stronger hydrogen-bonding with the urea moiety, and also with the quinone moiety of 1 receptor, and also the greater compatibility of the cavity of 1 with tetrahedral HSO₄^?.     

High temperature electrochemical studies using a channel flow cell heated by radio frequency radiation

Systems involving one and two electron redox reactions were studied under hydrothermal conditions using a novel hydrodynamic method based on a conventional channel flow cell where the working electrode was heated by radio frequency radiation. The diffusion activation parameters obtained with the radio frequency channel cell were compared with independent data from microelectrode high temperature experiments and analysed in terms of the Stokes–Einstein equation.     

Electrochemical reduction of N-thioamidoimidates: application to the synthesis of thiazolo[5,4-d]thiazoles

The reduction of N-thioamidoimidates (1) has been examined in aprotic media at a mercury electrode. As shown by cyclic voltammetry at fast scan rates and controlled potential electrolysis, an overall irreversible one electron transfer is followed by a rapid second order chemical reaction leading to a dimer which involves to thiazolo[5,4-d]thiazole by intramolecular cyclization.     

A theoretical study of the electrochemical reduction of oxygen1

Multi-dimensional potential energy surfaces have been constructed for the experimentally found most probable rate-determining step in electroreduction of oxygen on Pt(111) and Pt(100) using a combination of experimental data in Morse functions and ASED-MO (a semi-empirical quantum mechanical technique). The minimum energy path for the reaction has been extracted by Euler's single step method. In agreement with the position of Schmickler [W. Schmickler, Interfacial Electrochemistry, Oxford University Press, 1996] for atom transfer reactions, the Marcus continuum model (in which the Gibbs energy is related to rearrangements among the solvent molecules by means of quadratic expressions) has been avoided. Instead the interaction of the proton with the librating solvent molecules in its environments is described by model considerations (ion–dipole and ion–ion induced dipole interactions). A treatment of non-adiabacity has been made by means of Landau–Zener formalism and the quantum properties of the proton are taken into account using an Eckart barrier for the calculation of tunneling. On this basis, the kinetic parameters, e.g. the activation energies, entropies of activation, the symmetry factors and reaction rates of the model reaction, have been calculated.     

Electrodeposition of Au from [EMIm][TFSA] room-temperature ionic liquid: An electrochemical and Surface-Enhanced Raman Spectroscopy study

In this paper we report in situ Surface-Enhanced Raman Scattering (SERS) experiments carried out during the electrochemical deposition of gold from Au(I) cyanocomplexes in the room-temperature ionic liquid (RTIL) 1-ethyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl) amide ([EMIm][TFSA]). The obtained SERS spectra indicated the co-adsorption of CN⁻ and both anions and cations of the RTIL in the range from −1.8 to +0.3 V vs. an Au quasi-reference electrode (QRE). The surface CN⁻ peak exhibits a Stark tuning of ca. 28 cm⁻¹ V⁻¹. The oxidation of CN⁻ to OCN⁻ was observed at potentials more anodic than 0.3 V. The study was complemented by cyclic voltammetry, pinpointing RTIL reactivity at an Au electrode as well as CN⁻ adsorption effects and Au(I) reduction. SEM observations allowed to identify the conditions for the achievement of continuous Au films as well as the morphological peculiarities of Au electrodeposited from [EMIm][TFSA]. XPS measurements proved that no RTIL is incorporated into the Au film, under the investigated conditions.     

The electrode reactions of Fe(CN)63− and Fe(CN)64− ions studied at temperatures below the melting point of stoichiometric electrolytes

The electrode reactions of Fe(CN)₆^3? and Fe(CN)₆^4? ions have been studied at temperatures below the melting point of stoichiometric electrolytes. Tetramethylammonium cation hydrates: (CH₃)₄NOH·nH₂O(n = 5, 7.5, 10) and (CH₃)₄NF·4H₂O were selected as electrolytes. The redox active ion with higher electric charge, Fe(CN)₆^4?, is more stable at temperatures below as well as above the melting point of these electrolytes. However, the temperature dependence of the redox potential of the Fe(CN)₆^3?/Fe(CN)₆^4? couple is more pronounced in these conditions. In the limited temperature range below the electrolyte melting point the kinetics of the reaction are controlled by the rate of reactant transport towards the electrode surface. The apparent diffusion coefficient of redox active ions does not change substantially at temperatures around the electrolyte melting point. The activation energy of reactant transport is twice as large in frozen than in liquid electrolyte. It has been concluded that the motion of the redox active ions is restricted to a limited volume—the intergrain space of the electrolyte. This conclusion is supported by results of experiments performed in a cell filled with chemically inert beads and liquid electrolyte.     

Effects of FMLP and LPS on [Ca2+]i of peritoneal exudate polymorphonuclear leukocytes following onset of inflammation

Because a general study of activated neutrophils may have relevance to periodontal diseases and accompanying inflammation, we studied a function of mouse polymorphonuclear leukocytes (PMNs) that exude into the peritoneal cavity in response to inflammation caused by i.p. injection of 2% casein. The effects of E. coli -lipopolysaccharide (E-LPS) and a chemotactic factor, N-for-myl-N-methionyl-N-leucyl-L-phenylalanine (FMLP), on the level of intracellular calcium ([Ca²⁺]i) in these PMNs were examined. From analysis made with a laser cytometer (ACAS 570), the PMNs in exudates harvested 3–9 h after the onset of inflammation were shown to undergo [Ca²⁺]i elevation in response to 10^–6 M FMLP. The peak concentration of [Ca²⁺]i elicited by FMLP was highest in exudate cells 6 h after casein injection. In addition, about 65% of the PMNs in the 3-h exudate were FMLP sensitive displaying an elevated [Ca²⁺]i, whereas more than 85% of them in 6- and 9-h exudates became FMLP sensitive. Also, the maximum level of [Ca²⁺]i after FMLP stimulation was potentiated by pretreatment of the cells with E-LPS (0.2 μg/ml). The present study suggests that PMNs induced by casein injection and appearing in mouse peritoneal exudate at different times possess significantly different ability to undergo [Ca²⁺]i elevation, and different susceptibility toward a chemotactic factor, FMLP.     

The electrochemical oxidation of 2-amino-3-cyano-4-phenylthiophene: evidence for a new class of photoluminescent material

The electrooxidation of 2-amino-3-cyano-4-phenylthiophene on platinum electrodes was investigated for the first time in acetonitrile by cyclic voltammetry, controlled potential electrolysis, and spectrometric methods. The voltammetric responses were similar to those of common aromatic amino compounds. Two types of dimers were observed as intermediates in the early stages of oxidation. Ethlyamine and phenol were added to an electrolytic solution in order to determine the electrochemical behavior of 2-amino-3-cyano-4-phenylthiophene under basic and acidic conditions. We propose an E(CE)_n mechanism to account for this electrochemistry. 2-Amino-3-cyano-4-phenylthiophene is first oxidized to a cation radical, followed by chemical coupling to form dimers, which are electroactive. Controlled potential electrolysis gave a new class of π-conjugated oligoaminothiophenes exhibiting an absorbance at 432 nm and photoluminescence at 538 nm.     

前列腺素E2和白三烯B4对口腔癌促进作用的研究

目的通过在DMBA诱导的金黄地鼠口腔癌颊囊模型上,局部应用白三烯n4（LTB4）或前列腺素E2（PGE2）,探讨LTB4和PGE2在口腔癌形成中的作用,进一步阐明口腔癌的发病机制。方法用DMBA涂抹金黄地鼠左侧颊囊粘膜4周,第五周开始分别局部涂抹LTB4和PGE220周,处死动物,取全部颊囊进行肉眼观察计数和组织学检查,并进行统计学分析。结果LTB4＋DMBA组癌变率为51.4％（18／35）;PGE2＋DMBA组癌变率为45.7％（16／35）,均显著高于DMBA组20.0％（7／35）。另外两组不使用DMBA启动,同时局部分别涂抹LTB4和PGE220周,两组均有异常增生发生,但是没有癌变。结论PGE2和LTB4是口腔癌形成的促进剂,并且有可能成为化学预防作用的重要靶点。     

Novel studies on the electrochemical oxidation of 2-[4-(N,N-dimethylamino)phenyl]-6-methyl benzothiazole (DPMB) in acetonitrile at platinum electrodes

The electrochemical oxidation mechanism of 2-[4-(N,N-dimethylamino)phenyl]-6-methyl benzothiazole (DPMB) is studied in a 0.1 M N(C₄H₉)₄ClO₄ + acetonitrile (ACN) reaction medium by cyclic (CV) and square wave voltammetries (SWV) as well as by controlled potential bulk electrolysis at platinum electrodes. The primary radical cation formed by the one electron oxidation of DPMB undergoes a deprotonation process, which is the rate-determining step, followed by a radical–radical coupling. On the other hand, an initial quasi-reversible monoelectronic charge transfer mechanism is inferred from cyclic and square wave voltammograms recorded at scan rates and frequencies higher than 0.4 V s^?1 and 40 Hz, respectively. Diffusion coefficients of DPMB at different temperatures were calculated from the quasi-reversible convoluted cyclic voltammograms. DigiSim® and COOL software were used to fit the quasi-reversible cyclic and square wave voltammetric responses, respectively. Formal potentials, formal rate constants and positive transfer coefficients at different temperatures were evaluated from the fitting of cyclic voltammograms. The experimental activation parameters were also determined. The effects of the analytical concentration of the reagent and the temperature, as well as the addition of trifluoracetic acid and a strong base such as lutidine on the electrochemical responses are discussed. A general reaction mechanism as well as probable structures for dimeric products are proposed.Besides, the presence of an acid–base equilibrium in DPMB solutions is also studied by employing UV–Vis spectroscopic measurements at different trifluoracetic acid concentrations. An apparent value of (1.5 ± 0.2) × 10³ M^?1 was estimated for the DPMB basic constant at 20.0 °C     

The electrochemical behavior and surface analysis of Ti50Ni47.2Co2.8 alloy for orthodontic use

OBJECTIVES: The aim of this study was to investigate the electrochemical behavior of Ti50Ni47.2Co2.8 alloy in deaerated artificial saliva solutions with binary NiTi alloy as reference and to characterize the composition and structure of the passive film after polarization tests. METHODS: The corrosion behavior of NiTiCo alloy was systematically studied by open circuit potential, potentiodynamic and potentiostatic techniques. The surface characterization after anodic polarization tests were demonstrated by XPS. The electrolytes were maintained at 37 degrees C by immersing the test cell in water bath. 500 mV vs. SCE was applied on the samples for potentiostatic tests. The metal ions concentration was measured by ICP/OES. RESULTS: Potentiodynamic and potentiostatic tests results showed that the corrosion behavior of NiTiCo was similar to that of NiTi alloy. With the increase of pH value of the electrolytes, both corrosion potential (Ecorr) and pitting corrosion potential (Eb) decreased. XPS results revealed that the outmost passive film consisted mainly of TiO2 which were identical with that of NiTi alloy. The Ni ion release amount of NiTiCo was very close to that of NiTi alloy as examined by ICP/OES. Neither Ti nor Co ion was detected due to the detection limitation. SIGNIFICANCE: The corresponding relationship between corrosion behavior and pH value of the artificial saliva should be taken into consideration during the application of orthodontic wires. The addition of Co had little effect on the corrosion behavior of NiTi as well as the formation of the passive film.     

CXCL12/CXCR4在涎腺腺样囊性癌嗜神经侵袭中的作用

目的:探讨CXCL12/CXCR4在人涎腺腺样囊性癌嗜神经侵袭机制中的作用。方法:在基因水平上,应用real-timePCR法检测人施万细胞(human Schwanncell,HSC)和涎腺腺样囊性癌ACC-3细胞中趋化因子CXCL12及其受体CXCR4的表达。在蛋白水平上,应用流式细胞术检测HSC和ACC-3细胞膜上CXCR4的表达。应用ELISA检测HSC培养上清液中CXCL12的表达。应用趋化实验观察HSC培养上清液对ACC-3细胞的趋化作用。结果:HSC中CXCL12基因有较高的表达,而ACC-3细胞中表达量极少;HSC和ACC-3细胞中CXCR4基因均有表达。HSC和ACC-3细胞膜上CXCR4蛋白均有表达;HSC培养上清液中CXCL12蛋白的质量浓度约为(403.4±16.4)～(785.3±32.3)pg/mL;HSC培养上清液能够对ACC-3细胞产生趋化作用,应用CXCR4单克隆抗体或CXCR4受体激活拮抗剂AMD3100能明显抑制这种作用。结论:CXCL12/CXCR4可能与涎腺腺样囊性癌嗜神经侵袭有关。     

Synthesis and electrochemical characterizations of nano size Ce doped LiMn2O4 cathode materials for rechargeable lithium batteries

LiCe_xMn_2−xO₄ (x = 0.00–0.10) cathode materials for rechargeable lithium-ion batteries were synthesized by simple sol–gel technique using aqueous solutions of metal nitrates and succinic acid as the chelating agent. The gel precursors of metal succinates were dried in vacuum oven for 10 h at 120 °C. After drying, the gel precursors were ground and heated at 900 °C. The structural characterization was carried out by X-ray powder diffraction and X-ray photoelectron spectroscopy to identify the valence state of Mn and Ce in the synthesized materials. The sample exhibited a well defined spinel structure and the lattice parameter linearly increased with increasing the cerium contents in LiCe_xMn_2−xO₄. Surface morphology and particle size of the synthesized materials were determined by scanning electron microscopy and transmittance electron microscopy respectively. Electrochemical properties were characterized for assembled Li/LiCe_xMn_2−xO₄ coin type cells using galvanostatic charge/discharge studies at 0.5C rate and cyclic voltammetry in the potential range between 2.75 and 4.5 V at a scan rate of 0.1 mV s⁻¹. Among them cerium doped spinel LiCe_0.05Mn_1.90O₄ has improved structural stability, high reversible capacity and excellent electrochemical performance of rechargeable lithium batteries.     

The effect of FIV infection on CD4+ and CD8+ counts in periradicular lesions

AIM: The purpose of this study was to elucidate whether a decrease/increase in T-cell populations is present in the development of periradicular disease in the immunocompromised feline model. METHODOLOGY: Eight cats were immunosuppressed with steroids prior to infection with feline immunodeficiency virus (FIV). Another eight cats, age and sex matched littermates, were monitored and tested at equivalent periods of time and served as uninoculated, seronegative controls. Periradicular lesions were induced using local bacterial inoculations into the pulp of the canine teeth and assessed after one- and four-week periods, corresponding to the acute and chronic stages of the periradicular disease. Block sections were obtained and specimens were prepared for H & E and immunohistochemical staining for CD4+ and CD8+ receptors. Cells were quantified using a computer imaging system and data analysed using generalized estimating equation (GEE) regression models. RESULTS: Significantly lower CD4+ counts and CD4+/ CD8+ ratios were observed at all time periods in the periradicular region of the FIV group (P = 0.0006). No significant difference in CD8+ counts was observed between the two groups. In both groups there was a significant difference in the CD4+ counts between one week and baseline, and 1 week and 4 weeks. There was no significant difference between baseline and 4 weeks for either group. CONCLUSION: FIV infection reflected decreased CD4+ counts at the periradicular level, however, inflammation and progression of the lesion, appeared to be comparable to the non-immunocompromised controls.     

Anodic oxidation of free nitric oxide at gold electrodes modified by a film of trans-[Ru(III)(NH3)4(SO4)4pic]+ and molybdenum oxide

Gold surfaces were modified with an electrochemically deposited layer of non-stoichiometric molybdenum oxides. At these surfaces, trans-[Ru(III)(NH₃)₄(SO₄)4pic]⁺ complex was incorporated in a controlled way by cycling the potential consecutively in the range +0.50 to ?0.25 V at pH 2.6. Very reproducible voltammetric curves corresponding to the electrochemical process of the ruthenium complex were obtained, confirming the immobilisation of the material into the molybdenum oxide film. The anodic oxidation of nitric oxide (NO) at pH 7.4 was investigated at the modified electrode containing the molybdenum oxide+trans-[Ru(III)(NH₃)₄(SO₄)4pic]⁺ complex and an enhancement in the current response was observed compared with the signal at a bare electrode. The rate for NO electrochemical oxidation was dependent on the amount of catalytic ruthenium sites dispersed into the molybdenum oxide film. A linear relationship between current signals measured by square wave voltammetry and NO concentration was obtained in the 0–10 μM range. The applicability of the modified electrode as a sensor for real-time NO monitoring was also demonstrated.     

Up-regulation of vascular endothelial growth factor expression by adenosine through adenosine A2 receptors in the rat tongue treated with endotoxin

The main focus of the present investigation is to evaluate a differential effect of adenosine on the up-regulation of vascular endothelial growth factor (VEGF) expression through adenosine A₂ receptors in the rat tongue treated with endotoxin (lipopolysaccharide: LPS). Angiogenesis in the rat tongue treated with LPS/incomplete Freund's adjuvant (IFA) or endotoxin/IFA/adenosine A₂ receptor (A₂R) antagonists was examined using immunohistochemistry for LYVE-1, ED1, ED2, OX6, langerin and VEGF, and real-time polymerase chain reaction (PCR) for VEGF. The distributional density of both blood vessels and OX6⁺ cells was significantly increased at day 8 after injection of LPS/IFA. The immunoreactive products of VEGF were intensely labelled in the cytoplasm of various antigen presenting cells (APCs) including dendritic cells (DCs) with double-immunofluorescence technique. Increase in VEGF mRNA expression level, the occupancy ratio of blood vessels, and the number of ED1⁺, ED2⁺, OX6⁺, and langerin⁺ cells was inhibited in the injured tongue of rats as a consequence of the treatment with A₂R antagonists. The present results indicate that the LPS-induced adenosine might promote angiogenesis by the up-regulation of VEGF expression in macrophages/DCs through A₂ receptors. This suggests that the synergistic interaction between toll-like receptor (TLR) and A₂ receptor signalling observed in vivo plays an important role in oral mucosal wound healing.